score:2

Accepted answer
var list = new list<dynamic>
{
    new {userid="simone", networks = "cmt,mtt,mvv"},
    new {userid="curtink", networks = "mtr,nan,nog"},
    new {userid="jamesl", networks = "cmt,logo,cmdy"},
    new {userid="bondineg", networks = "tvl,tvlc,nktn"}
};
var users = string.join(",", list.where(d => d.networks.contains("cmt"))
                                 .select(u => u.userid));

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